B I R 



nightly enlarged at the extremities. It is direfled forwards 

 and inwards, and at the anterior extremity touclies the ■ntc''- 

 articular bone of the oppofite fiiie : at tliis p'ace the ends df 

 both are placed againll the pofterior cxtrt- mity of the pala- 

 tine hones, and arc liollowcd fo as to cncompafs the lower 

 edge of the feptiim of the orbits, along which they hdve 

 foir.e degree of motion, when urged forwards by the arti- 

 cular bones. 



The effcft of thi". mechanifm is, that whenever the inferior 

 end of the articular hone is brought forwards, which is ac- 

 compliflicdin a dearnc by the opening of the lower jaw, but 

 ftill more by particular mufcies, to be hereafter defcrib.'d, 

 the inter-articular bones prtfs againft the extremity of the 

 palatine bones, and they communicate the impulfc to the 

 ■whole fupcrior mandible, which being very thin at its junc- 

 tion with the OS frontis, fufFers itfelf to be puflied up or ele- 

 vated fro!n the line it commonly holds, and in this manner 

 the mouth of birds is dilated in part by the motion of the 

 upper as well as the lower jaw. 



The parro/ is remarkable for having a great degree of 

 motion in the upper mandible ; in this bird the fuperior 

 mandible is at all times feparate from the frontal bone, they 

 being only conncdled to each other by a very flexible liga- 

 ment. 



The i/ifrior mandible appears to be formed originally of 

 four pieces ; two of thcfc correfpond with the bones of the 

 inferior maxilla, and the others produce tlie mould on which 

 the lower part of the bill grows. The formation of the in- 

 ferior jaw, indepetuient of its conneftion witli the bill, differs 

 very much from that of mammalia. There are no condyles, 

 nor any procefs deferviiig the name of coronoid, and the 

 angle of the jaw is the thickeft and loweft part of it. The 

 articulation is made by two deprcfled furfaces placed on the 

 fide of a cavitv, into which the potterior pulley of the arti- 

 cular bone flips in the motions of the jaw. 



The form of the bones of the mandibles is precifcly the 

 fame of the horiicy bill, with which they are covered ; ex- 

 cept in fome lualer birds, the bill afl"umes more or lefs of a 

 conic figure ; fomctimes comprefTtd, fometimes arched, 

 in fome cafes elongated, in others fliort, and varj'ing in the 

 degree of (harpnefs, ftrength, and folidity. As the 

 diverlity, however, which occurs in the mandibles of birds, 

 is an external appearance, and belongs rather to the fcience 

 of natural hiilory, than to comparative anatomy, it would 

 be improper to difcufs the fubjeft in the prtfent article. 



The peculiarities of the fojfe AnA foramina of the face in 

 birds, depend chiefly upon the form and proportions of the 

 bones. 



The orlitar foflx are fo large, that they appear to occupy 

 the greatell part of the profile of the head of birds. They 

 extend in the flceleton from the roof of the fliull to the pa- 

 late, and communicate with the pofterior part of the orL'an 

 of fmell. Cuvicr very aptly compares them to the impref- 

 fion which one would conceive might be left by pinching 

 the flcuU between two fingers, provided it were in a foft 

 ftate. 



The nafal fojfx are continuous with the orbitar. They 

 open upwards by the two external nares, or noftrils, and 

 below by the pofterior nares. The feptiim nafi pro- 

 ceeds fo fliort a way in the nofe, that the nafal folTae make 

 but one cavity. The external apertures of the nares 

 are found in the bone, at the bafe of the convex furface of 

 the biU. 



T\\i temporal fojpi are not crofTed by the zygoma. They 

 vary in depth according to the ftrength of the mufcies em- 

 ployed in raifing the lower jaw ; they are therefore moft 

 plain in the rapacious birds, and thofe with longer heavy bills. 



B I R 



The fphno-maxillary fifure can have no exiftence in bird* 

 from th. fitrure a-.d extent of their orbits; neither have they 

 the in'.crnid orlitar, s.nA fub-orbitar foramina, or the fpheno- 

 palatine canal. 



The iiidfi've foramin:i are fmall and numerous in the heron, 

 flamingo, eagl; &c. There is but one of a moderate fize 

 placed near the bafe of the bill in the dud, the curajfozu, the 

 cormnrant, and the fpoon-bill, &c. In the cnJo'U)ary , the 

 foramen incifivum is fmall, and near the end of the mandible, 

 but in the oflrich it is of great lize. The florh has a long 

 flit, into which open an immenfe number of minute 

 holes. 



The OS hyoidcs poflciTes a finjular conformation in birds. 

 The body of the bone is in general of a fliort round figure, 

 fomewhat enlarged at its pofterior extremity, at which 

 place it is articulated with the two cornua. Thefe rcfemble 

 horns exaftly, both in their fliape and dir cftion ; they are 

 terminated by additional pieces, which form a fort of joint 

 with the principal part of the b.orn, and generally confift 

 entirely of cartilage. To the pofterior end of the body or 

 middle bone of the hyoides, there is articulated a fmall lly- 

 loid or dagger-fliaped bone, which proceeds diredly back- 

 wards, and foon terminate; in a point. There is alfo a 

 bone articulated with the anterior extremity of the body of 

 the hyoides, which penetrates the fubftance of the tongue, 

 and partakes in a certain degree of the form of that organ : 

 it is commonly ter.xinated by a pointed cartilage, which is 

 attached to it by a moveable joint, and is continued to near 

 the tip of the tongue. This bone we (hould choofe to call 

 the lingual. 



The OS hyoides and lingual bone are Angularly formed in 

 thofe birds which have the power of protruding their tongue 

 to take their food. In the ivoodpccktrs, for inftance, the car- 

 tilaginous extremities of the horns of the hyoides are im- 

 menfely long, and when the tongue is not proje<Scd, arc 

 lodged in a groove or furrow, which runs over the whole 

 head, and terminates only at the root of the bill. The lin- 

 gual bnne in thefe birds alfo is not cartilaginous at its extre- 

 mity, but is covered with a hard or horny fubftance, which 

 protrudes beyond the foft parts of the tongue for the di- 

 ftance of about the quarter of an inch, ending in a point, and 

 furnifhcd with a number of fharp barbs, or ipiculo;, whicii 

 are moveable in the pofterior direftion only ; fo that, like 

 the teeth of fome fifli, they fuffer the infects on which the 

 bird preys to be eafily perforated by the end of this inftru- 

 ment, but render it impolTible for them afterwards to retreat. 



The vertebrK of the different regions of the fpine 

 of birds do not bear the fame proportion to each other 

 with refpcft to number that is ufual in other animals. The 

 cervical portion in this clafs is generally compofed of a much 

 greater number of vertebrse than any other divifion of the 

 fpine. The length of the neck is in moft birds determined 

 by the height of the legs. Thofe nvater birdt, however, 

 which procure their fubfiftence by fifhing, are provided with 

 long necks, and at the fame time fhort limbs, as in the cor- 

 morant, divers, iSc. The dorfal vertebra are ufually lefs 

 numerous than in quadrupeds. The vertebra: of the loins 

 become anchylofed with the bones of the pelvis, and with 

 each other at an early peiiod, and confequeutly it is difficult 

 to reckon them. The caudal vertebras are moft numerous 

 in thofe birds which make the greateft ufe of the tail, fuch 

 as the fivalloiv, luoodpecker, oflrich, Cfff. 



The following table, which is extradled from Cuiver's 

 Leftures on Comparative Anatomy, exhibits the variety 

 which exifts with refped to the number of the vertebrx in 

 many fpecies. 



7ABLE 



